Communication: accurate determination of side-chain torsion angle ₁ in proteins: phenylalanine residues

Quantitative side-chain torsion angle χ₁ determinations of phenylalanine residues in Desulfovibrio vulgaris flavodoxin are carried out using exclusively the correlation between the experimental vicinal coupling constants and theoretically determined Karplus equations. Karplus coefficients for nine vicinal coupling related with the torsion angle χ₁ were calculated using the B3LYP functional and basis sets of different size. Optimized χ₁ angles are in outstanding agreement with those previously reported by employing x ray and NMR measurements.